负荷与混合方式对厌氧膜生物反应器中甲烷气-液分配特征的影响

Effects of load and mixing mode on methane gas-liquid distributioncharacteristics in anaerobic membrane bioreactors

厌氧膜生物反应器(anaerobic membrane bioreactors,AnMBR)出水普遍存在过饱和的溶解性甲烷(dissolved methane,DCH4),易造成能量流失和温室效应,阐明AnMBR中甲烷气-液分配特征对提高甲烷回收率具有重要意义。为此,本文研究了负荷和混合方式对AnMBR中甲烷气-液分配特征的影响。结果表明,在35℃,负荷为0.6~1.8 kg·(m^(3)·d)^(-1)的条件下,AnMBR实现了较好的有机物去除效果(COD去除率>90%),运行过程DCH4均处于过饱和状态(过饱和度为1.3~2.1),随着负荷的提升DCH4浓度升高,过饱和度有所下降;相比于循环混合,在浪式脉冲混合条件下的甲烷传质系数(KLa)更大,其中DCH4浓度、过饱和度及DCH4占进水COD的比例均较低。AnMBR大部分进水COD转化为甲烷,主要以气态形式存在(50.2%~60.0%)。浪式脉冲混合时反应器总能耗比循环混合降低了85.9%~88.0%,提升负荷有利于实现AnMBR处理废水过程的能量平衡。

Dissolved methane(DCH4)is commonly found in the effluent of anaerobic membrane bioreactor(AnMBR),thus easily causing energy loss and greenhouse effect.Understanding the characteristics of methane gas-liquid distribution is crucial to improve the methane recovery in AnMBR.This study investigates the effects of load and mixing mode on the methane gas-liquid distribution in AnMBR.The results showed that the AnMBR achieved favorable organic removal(COD removal>90%)at 35 oC and 0.6~1.8 kg·(m^(3)·d)^(–1)load,but DCH4 remained oversaturated(oversaturation ratio of 1.3~2.1)throughout operation.As the load was elevated,DCH4 concentrations also increased while the oversaturation ratios decreased.Wave-pulse mixing mode,with higher methane transfer coefficient(KLa),resulted in lower DCH4 concentration,oversaturation ratio and the proportion of DCH4 to influent COD compared with cyclic mixing mode.Most of the influent COD was converted to methane in gaseous form(50.2%~60.0%).The total energy consumption of reactor under wavepulse mixing mode was 85.9%~88.0%lower than that of cyclic mixing mode.Elevating load is prone to achieve a net energy balance during AnMBR wastewater treatment.